The thing is though,
right after liberation, the Russians started shitting the bed by sending incompetent fools (did Tsarist Russia even have anything else?) to Bulgaria to rule. Then they sponsored multiple coups against the first Prince of Bulgaria who they thought was a German puppet based on his origins, without even bothering to ask him. Then they sabotaged Bulgaria's unification and defence against Serbia efforts by abandoning the army. Then after a successful (in ousting the prince, but not in anything else because again, the people running it were as incompetent as it could be) coup, he was asked to return but he thought the only way he could would be with Russia's acceptance, which the Russia didn't give. Then Russia, for some weird reason only their incompetence can explain,
refused to recognise the regency council looking for a new head of state (which first went to them expecting them to nominate a Russian prince).
I could go on, but basically Russia's goodwill was spent in the first few decades of them incompetently and arrogantly bumbling around and making it extremely hard for the young optimistic nation which was really looking towards Russia as the big helpful brother and desperately needed help to survive.
Today you can also add 50 years of imposed socialism, which had its ups and downs (massive industrial, education, sport advancements) but was imposed and kept with tanks, and Russia's aggressive and imperialist foreign policy which directly results in tens of thousands of deaths. Why the fuck would anyone still think Russia is the good guys? This can only come out of blatant misunderstanding of history.